Room Stat

[Dan6206]

Hi
i had an engineer come out to diagnose a fault with my boiler which we thought was the 3 port valve not working, but was diagnosed to be the room stat not calling for the heating. on the advice of engineer he said change the stat as its cheap than them doing it at a cost of £140

I just wanted to know if i have wired it in correct as its still not calling for heating.

It is a Center EHE0200155 room stat
Earth to Earth Terminal
live goes in No1
neutral No3
and the other in No2
WHAT IS THE 3RD WIRE?
I tried swapping No2/No3 over but it trips electrics, so i guess above is correct.

on the diagram it shows between 1&4 that there is some kind of connection, Is this why its not calling for boiler??

I have enclosed some pics for reference, if someone can help that would be great.

Many Thanks

 

[THRIPSTER]

Between 1 & 3 is correct for call for heat.

Regards

 

[Dan6206]

Hi sorry to be dumb, but can u explain a bit more please?

 

[stem]

It all depends what each of the wires was used as by the original installer. Usually Blue will be neutral (Terminal 2) and the other two (Red and Brown) will be 'Live' and 'Switched Live' (terminal 1 is live, and terminal is 3 switched live) but which wire is used for which, will depend upon who installed the original thermostat.

However, if you have swapped wires around in an ad-hoc fashion, and 'tripped the electrics' you will have created a short circuit and possibly damaged another part of the system.

 

[bernardgreen]

live goes in No1
neutral No3
and the other in No2

Neutral goes to Terminal 2

Putting Neutral to Teminal 3 means the switch will be shorting ( connecting ) Live directly to Neutral ( why the MCB tripped out ) That short may have danaged the contacts in the switch in the thermostat.

The third wire from Terminal 3 to the rectangle in the diagram is the Call for Heat connection, The rectangle represents the heater / boiler that the thermostat is controlling.
Terminal 3 becomes Live when heating is required

 

[THRIPSTER]

When you turn the thermostat temperature up beyond the existing room temperature, the switch changes from its rest position 1 connected to 4 to 1 connected to 3. Neutral is connected to 2. In randomly swapping 2 & 3 you may have blown either the CH programmer or boiler PCB or both. Pin 4 is sometimes used in systems where you need a line connection to indicate that the heating is off.

Regards

 

[Dan6206]

Hi guys.
here is a picture of the wiring from how the old stat was wired in, can you relate in dummy terms what colour wires go from the old stat to what numbers they go to on the new stat.
when i changed the wires and got the wife to turn the electrics on thats when it tripped out and the program time had a little spark flash on it, could that
have fooked it? as it still comes on etc..

Thanks

 

[Taylortwocities]

I assume that the backplate in your hand is the new one?
Brown to L
Grey with blue sleeve to N
Black with brown sleeve to NO

But, as mentioned above, your messing around with the wiring may have blown something. It is suprising that the MCB tripped. There should be a 3amp fuse protecting the heating/boiler components. This is usually in an FCU near the boiler.

Check that some numpty hasnt got too big a fuse in there.
If you have blown something, then the engineer's £140 might have been a good deal!

You can test that the programmer & boiler have survived your murder attempt by just connecting the brown and the black conductors together (NOT THE GREY/BLUE ONE). That should fire the boiler when the programmer is set for heating ON.

 

[stem]

Are you really sure? your posed photo showing the original wiring, indicates that the blue sleeved wire (normally neutral) is going to the Live connection, and the brown wire going to the neutral terminal!!

 

[Taylortwocities]

I think the OP has just photod the new back plate and the three wires loose, not as an indication of their connection.

I am rather confused on this (should be simple) post.

From what I can see the Center EHE0200155 is the OLD stat. (or have I misunderstood?)
We don't know what the new one is, but the connections on both are clear enough.

 

[winston1]

If it is on a lighting circuit (we don't know) there would be no FCU. Anyway the fuse in any FCU is to protect the cable, not the boiler which will have its own internal fuse. The cable is rated at more than 3 amps so the fuse can be as well.

 

[Dan6206]

i do apologise, the back plate im holding is off the old room stat (the wires show how they were connected)
the second picture is of the new room stat.
what i want to know is what colour wire goes to what number in the 2nd picture which is of the new room stat

 

[Dan6206]

I assume that the backplate in your hand is the new one?
Brown to L
Grey with blue sleeve to N
Black with brown sleeve to NO

But, as mentioned above, your messing around with the wiring may have blown something. It is suprising that the MCB tripped. There should be a 3amp fuse protecting the heating/boiler components. This is usually in an FCU near the boiler.

Check that some numpty hasnt got too big a fuse in there.
If you have blown something, then the engineer's £140 might have been a good deal!

You can test that the programmer & boiler have survived your murder attempt by just connecting the brown and the black conductors together (NOT THE GREY/BLUE ONE). That should fire the boiler when the programmer is set for heating ON.

sorry for the ignorence what is the FCU?

 

[winston1]

As it stands we don't know which wire is which. Either the brown wire or the black sleeved brown could be the permanent live. Some investigation is needed. Remember this was originally wired by a plumber.

 

[securespark]

It looks like that post disconnection, but could it be that they have been in the correct terminals prior to removal then moved?